EP0769511B1 - Binder combination for the preparation of solvent-free coating masses - Google Patents

Description

a - einer Heteroallophanatgruppen enthaltenden Polyisocyanatkomponente und

b - einer lösungsmittelfreien Komponente mit isocyanatreaktiven Gruppen,

ihre Herstellung und Verwendung in 2K-Beschichtungsmaterialien.The invention relates to a binder combination for producing solvent-free coating compositions consisting essentially of

a - a polyisocyanate component containing heteroallophanate groups and

b - a solvent-free component with isocyanate-reactive groups,

their manufacture and use in 2K coating materials.

In addition to epoxy systems, building protection is specially designed for high-quality elastic Coatings Binder combinations made from polyisocyanates and isocyanate-reactive Components such as polymer polyols used. Are required here coatings with high layer thickness, which means the use of solvent-based Largely excludes products.

Binder combinations based on solvent-free aliphatic polyisocyanates have excellent yellowing stability. Compared to polyisocyanates with aromatically bound isocyanate groups, however, they show one slow curing. Furthermore, coatings are mostly used obtained low hardness.

Aromatic polyisocyanates show in the binder combinations with polymer polyols rapid hardening and hardness development. However, only with special hydrophobic polyester polyols for bubble-free curing in higher Layer thicknesses possible.

The required low viscosity of the polyisocyanate component can be found in the previously used aromatic systems only by dilution with monomers Meet diisocyanates. From a toxicological point of view, only products come for this based on diisocyanatodiphenylmethane in question. These are based on polyols Castor oil base combined used as a coating combination. Owing to this binder combination cannot directly provide insufficient saponification stability can be applied as a 2K system to basic substrates. The application remains limited to intermediate layers and cover layers.

Polyisocyanates containing allophanate groups based on aliphatic or aromatic diisocyanates have long been known, e.g. GB-A-994 980, EP-A-303 150, EP-A-194, DE-A-2 009 179 and 2 040 645 and in US-A-3 769 318.

Solvent-free binder combinations that work quickly even in thick layers cure to bubble-free coatings with good hardness levels, however, are in the mentioned disclosures are not described. The ones listed in the Patent applications claimed polyisocyanates with aromatically bound isocyanate groups, based on compounds containing homoallophanate groups, as well as the listed aliphatic polyallophanates are due to the slow Hardening, too high intrinsic viscosity and too high susceptibility to blisters in binder combinations not suitable with polyols.

We are therefore looking for solvent-free solutions, especially for concrete sealing Binder combinations that quickly become bubble-free even in thick layers React coatings with a good level of hardness.

This object could be achieved by the binder combination according to the invention from a low-viscosity isocyanate-reactive component and solvent-free Dissolved aromatic polyisocyanates containing heteroallophanate groups become.

According to the invention are polyisocyanates containing "heteroallophanate groups" Understand products whose predominant proportion of allophanate groups is composed of an aliphatic and an aromatic isocyanate group.

In contrast, under "homoallophanate groups" polyisocyanates To understand compounds whose allophanate groups consist of two aliphatic or two aromatic isocyanate groups have arisen.

a) einer Polyisocyanatkomponente mit aromatisch gebundenen Isocyanatgruppen,

b) einer lösungsmittelfreien Komponente mit isocyanatreaktiven Gruppen und

c) gegebenenfalls weiteren Hilfsmitteln und Zusatzstoffen,

dadurch gekennzeichnet, daß die Komponente a) besteht aus Heteroallophanatgruppen enthaltenden Polyisocyanaten

i) eines NCO-Gehaltes von 3 bis 16 %,

ii) einer mittleren Funktionalität von 1,8 bis 4,

iii) eines Allophanatgruppengehaltes (berechnet als C₂HN₂O₃, MG: 101) von 5 bis 35 % und

iiii) eines Gehaltes an Kohlenwasserstoffketten (linear, verzweigt, gesättigt oder ungesättigt), die über ein Sauerstoffatom gebunden vorliegen, mit im Mittel von 2 bis 23 Kohlenstoffatomen von 10 bis 65 %.

The invention therefore relates essentially to solvent-free binder combinations consisting of

a) a polyisocyanate component with aromatically bound isocyanate groups,

b) a solvent-free component with isocyanate-reactive groups and

c) optionally further auxiliaries and additives,

characterized in that component a) consists of polyisocyanates containing heteroallophanate groups

i) an NCO content of 3 to 16%,

ii) an average functionality of 1.8 to 4,

iii) an allophanate group content (calculated as C ₂ HN ₂ O ₃ , MW: 101) of 5 to 35% and

iiii) a content of hydrocarbon chains (linear, branched, saturated or unsaturated), which are bound via an oxygen atom, with an average of 2 to 23 carbon atoms of 10 to 65%.

The invention also relates to the production and use of the Binder combinations in or as 2-component coatings.

i) NCO-Gehalt von 3 bis 16, vorzugsweise 5 bis 13 und besonders bevorzugt 7 bis 10,5 %,

ii) eine mittlere Funktionalität von 1,8 bis 4, vorzugsweise 1,9 bis 3 und besonders bevorzugt von ca. 2,0,

iii) einen Allophanatgruppengehalt (berechnet als C₂HN₂O₃, Molekulargewicht MG: 101) von 5 bis 35 bevorzugt 10 bis 23 und

iiii) einen Gehalt an Kohlenwasserstoffketten, die über Sauerstoff an Allophanatgruppen gebunden vorliegen, mit im Mittel 2 bis 23 Kohlenstoffatomen von 10 bis 65 %, vorzugsweise 18 bis 53 % und besonders bevorzugt 30 bis 53 %.

In the binder combinations according to the invention, the polyisocyanate component a) has one

i) NCO content of 3 to 16, preferably 5 to 13 and particularly preferably 7 to 10.5%,

ii) an average functionality of 1.8 to 4, preferably 1.9 to 3 and particularly preferably of approximately 2.0,

iii) an allophanate group content (calculated as C ₂ HN ₂ O ₃ , molecular weight MG: 101) of 5 to 35, preferably 10 to 23 and

iiii) a content of hydrocarbon chains which are bonded to allophanate groups via oxygen and have an average of 2 to 23 carbon atoms of 10 to 65%, preferably 18 to 53% and particularly preferably 30 to 53%.

The hydrocarbon chains can be linear, branched, unsaturated or be saturated. Preferably hydrocarbon chains with an average of 8 to 23 carbon atoms and particularly preferably with an average of 16 to 23 carbon atoms used.

The carbon atoms in the hydrocarbon chain can also be derived from oxygen atoms available separately.

The coating combinations used according to the invention are produced Polyisocyanate component a) by reaction of a linear aliphatic diisocyanate component a1) with a hydroxyl component a2) in an NCO / OH ratio from 1.0 to 0.5, preferably 1.0 to 0.6 and particularly preferably from 1.0.

The reaction is preferably in a temperature range of 40 to 140 ° C 60 to 120 ° C carried out.

The resulting compounds or mixtures containing urethane groups have an average molecular weight of 250 to 4000, preferably 300 to 2000 and particularly preferably 300 to 1000 g / mol.

If an excess of hydroxyl component a2) is used in the urethanization, some of the hydroxyl component a2) remains in the reaction product. In This excess portion (or parts thereof) can be used in a process variant Hydroxyl component a2) also only after the addition of the diisocyanate component a3) are added. This portion then reacts with the diisocyanate component a3) to urethane and further to allophanate.

The urethane produced from a1) and a2) can also be made from that of the isocyanate component a1) underlying amine via phosgene-free known in the literature Urethane syntheses are produced, as described, for example, in EP-A-27 940, EP-A-27 952, EP-A-27 953, EP-A-323 514 and EP-A-355 443 are mentioned. This is however less preferred.

The reaction of the urethane component from a1) and a2) with the diisocyanate component a3) takes place in an NCO / urethane equivalent ratio of 3: 1 to 100: 1 preferably from 6: 1 to 60: 1 and particularly preferably from 8: 1 to 30: 1 in one Temperature range from 20 ° C to 150 ° C, preferably 50 ° C to 120 ° C and especially preferably 60 ° C to 90 ° C, preferably to accelerate the allophanatization reaction Usual catalysts known in the literature can be used.

Examples of catalysts which can be used are tetraalkylammonium hydroxides or Arylalkylammonium hydroxides, metal salts such as iron (III) chloride, potassium octoate, Zinc compounds such as zinc stearate, zinc octoate, zinc naphthenate, zinc acetylacetonate, Tin compounds such as tin (II) octoate, tin (II) ethylhexanoate, tin (II) laurate, Aluminum tri (ethlylacetoacetate), dibutyltin oxide, dibutyltin dichloride, dibutyltin diacetate, Dibutyltin dilaurate, dibutyltin maleate or dioctyltin diacetate, Manganese, cobalt and nickel compounds as well as mineral acids such as trifluoroacetic acid, Sulfuric acid, hydrogen chloride, hydrogen bromide, phosphoric acid and perchloric acid and any mixtures.

In the reaction of urethane groups with aromatic isocyanate compounds strong acids, as described in EPA-194, can also be used. However, this is less preferred.

The catalysts can be before the allophanatization reaction or even before be added to the urethanization. They come in concentrations of 0.001% to 5%, preferably 0.005% to 1% is used. The catalyst can, if possible, be removed from the reaction mixture by distillation. It can However, it also makes sense to use suitable catalyst poisons (e.g. water, acid chlorides) to stop its catalytic action.

After the allophanatization reaction, the excess, distillable Starting diisocyanate a3) preferably by thin-film distillation except for a residual content in the process product of less than 0.5, preferably less than 0.2 % By weight removed. Preferably heteroallophanates with aromatically bound isocyanate groups of the type described have sufficient thermal stability in order to remove excess component a3) not to be broken down to a large extent in urethane and diisocyanate.

As diisocyanate component a1) with aliphatic isocyanate groups, linear aliphatic, branched diisocyanates with an NCO content of 30 to 60%, preferably 40 to 60% are used. Examples include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (HDI), 2,2,4-and 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,11-diisocyanatoundecane, dodecamethylene diisocyanate as well as their mixtures.

For modification, up to 20 mol% can also be mono- and higher functional isocyanate compounds such as butyl isocyanate, stearyl isocyanate and Find 2-ethylhexyl isocyanate. However, this is by no means preferred.

1,6-Diisocyanatohexane is very particularly preferred as the diisocyanate component or 1,4-diisocyanatobutane or mixtures thereof.

Alcohol or mixtures of alcohols can be used as alcohol component a2) with an average hydrocarbon chain of 2 to 23, preferably 8 to 23 and particularly preferably 16 to 23 carbon atoms, which are linear, branched, can be saturated and unsaturated.

The OH functionality of the alcohol component is between 1 and 1.5, preferably 1 and 1, 2 and particularly preferably 1.

Examples include methanol, ethanol, n-propanol, isopropanol, methoxypropanol, isomeric butanols, pentanols, hexanols, heptanols, octanols, nonanols, decanols, dodecanols, octadecanols, ^R Lorol types, saturated fatty alcohols and mixtures.

When mixed with monofunctional alcohols, higher functional ones can also be used Alcohol components are also used. Examples of these are ethylene glycol, 1,2-propanediol and 1,3, 1,4-butanediol and 1,3, 1,6-hexanediol, 1,8-octanediol, Nonandiol-1.9, decanediol-1.10, dodecanediol-1.12, octadecanediol-1.12, neopentyl glycol, 1,4-bishydroxymethylcyclohexane, 2-methyl-1,3-propanediol, 2,2,4-trimethylpentanediol-1,3, 2-ethyl-1,3-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, Dipropylene glycol, tripropylene glycol, dimer fatty alcohols, trimer fatty alcohols, Glycerin, trimethylolpropane (TMP), trimethylolethane, the isomers Hexanetriols, polyethers up to an average molecular weight of 4000 g / mol as well as mixtures.

Unsaturated alcohols such as trimethylolpropane diallyl ether can also be used, isomeric butenols and monofunctional alcohols, which differ from corresponding ones Acids or acid mixtures of unsaturated synthetic and natural fatty acids derived. Examples of naturally occurring fatty acid mixtures are those made from castor oil, peanut oil fat, cottonseed oil, safflower oil, wood oil, soybean oil, sunflower oil, Linseed oil, rape oil, valley oil, sperm oil and herring oil derived acids.

In addition to such unsaturated monofunctional alcohols, the alcohol component a2) also reaction products from the unsaturated or saturated fatty acids with epoxy compounds such as ethylene oxide, propylene oxide, Butylene oxide, styrene oxide and 2-ethylhexyl oxide are used.

Finally, transesterification products can also be used as alcohol component a2) Fatty acid based triglycerides with higher polyols like glycerin, Trimethylolpropane, pentaerytrite and sorbitol can be used. Such products then contain in addition to unreacted triglycerides mono-, di- and trivalent Alcohol components.

The hydrocarbon chain can optionally be interrupted by oxygen atoms his.

As diisocyanate component a3) with aromatically bound isocyanate groups come diisocyanates or mixtures with an NCO content of 35 to 53, preferably 40 to 50%. Among others, here are the Isomers of tolylene diisocyanates, naphthylene diisocyanates and phenylene diisocyanates as well as mixtures.

To achieve a special property level, monoisocyanates, such as phenyl isocyanate or triisocyanates up to one Use content of 20 mol%.

Preferred component a3) is 2,4- or 2,6-tolylene diisocyanate or their Mixtures used.

Component b) consists of at least one compound with at least two groups reactive towards isocyanate groups or at least two Groups which can be converted hydrolytically into such groups. If applicable, the Use of such compounds, both free and such reversibly blocked groups that are reactive towards isocyanate groups have, possible. It is also possible to use different ones such compounds, including those mixtures which are both compounds with free as well as compounds with reversibly blocked towards isocyanate groups have reactive groups.

The compounds of component b) preferably have an average per molecule 2 to 6 free or blocked groups that are reactive towards isocyanate groups on. The molecular weight of component b) can vary within a wide range. Preferably low molecular weight compounds, i. H. such with a molecular weight of about 100 to 600 used.

The amount of component b) is otherwise measured so that in the binders the molar ratio of isocyanate groups of component a) to free and / or reversibly blocked, reactive towards isocyanate groups Groups of component b) at 0.8: 1 to 10: 1, preferably 0.9: 1 to 4: 1, in particular 1: 1 to 2: 1 and particularly preferably 1: 1 to 1.2: 1.

• Polyoxazolidine der aus Polyurethanchemie an sich bekannten Art (z.B. DE-A-2 018 233, DE-A-2 446 438);
• Polyketimine oder Polyaldimine der aus der Polyurethanchemie an sich bekannten Art, (z.B. DE-A-1 520 139, DE-A-3 308 418);
• aromatische Polyamine, insbesondere Diamine mit sterisch gehinderten Aminogruppen (z.B. US-A-4 218 543) als Kettenverlängerungsmittel

und/oder

• mehrwertige Alkohole des Molekulargewichtsbereichs 62 bis 1000, vorzugsweise 62 bis 399, besonders bevorzugt 400 bis 1000.

Examples of components b) or part of component b) are:

• Polyoxazolidines of the type known per se from polyurethane chemistry (for example DE-A-2 018 233, DE-A-2 446 438);
• Polyketimines or polyaldimines of the type known per se from polyurethane chemistry (for example DE-A-1 520 139, DE-A-3 308 418);
• aromatic polyamines, especially diamines with sterically hindered amino groups (for example US Pat. No. 4,218,543) as chain extenders

and or

• polyhydric alcohols in the molecular weight range 62 to 1000, preferably 62 to 399, particularly preferably 400 to 1000.

Suitable low molecular weight alcohols are, for example, ethylene glycol, propylene glycol, 1,4-butanediol, glycerol, trimethylolpropane, pentaerythritol, diethylene glycol, Dipropylene glycol or mixtures of such polyols. Suitable higher molecular weight Alcohols are, for example, polyhydroxy compounds such as epoxy resins, phenolic resins, Alkyd resins, castor oil, hydroxyl group-containing polyester resins, silicone resins, Polyacrylates, polyethers, polycarbonates and mixed types.

To produce the binder combination, the individual components a) and b) and optionally c) mixed together. In case of use of compounds b) with reversibly blocked isocyanate-reactive groups Connections, this creates storage-stable coating combinations, which are stable in the absence of moisture and after application to a cure suitable substrate quickly in the presence of moisture. if necessary the hardening reaction can also be carried out by adding known per se Catalysts such as p-toluenesulfonic acid, dibutyltin octoate or Zinc chloride can be accelerated.

In the case of the use of reactive components b), the free isocyanate groups reactive groups, i.e. especially amino or hydroxyl groups the binder combination has only a limited pot life and should be processed within this time.

Incidentally, the term "binder combination" used here is to that effect to understand that the binders of the invention from the individual components a) and b) exist, the individual components when using a blocked individual component b) can also be combined to form a "one-pot system" can.

Are preferably used as component b) with blocked and / or free isocyanate-reactive Groups of hydroxy-functional polyethers, polyesters, polycarbonates and polyacrylates or mixtures and mixed types are used, particularly preferably hydroxyl-containing polyethers are used.

The binder combination of polyisocyanate component a) according to the invention and component b) of the type mentioned by way of example, as such, i.e. H. without Use of other auxiliaries and additives c) as a coating agent or sealing compounds can be used. They are preferably used however in combination with auxiliaries and additives c) of the type known per se.

As further auxiliaries c) in the coating materials according to the invention for example the usual plasticizers such as tricresyl phosphate, phthalic diesters or chlorinated paraffins, wetting agents, leveling agents, skin preventing agents, Anti-foaming agents, matting agents such as silica, Aluminum silicates and high-boiling waxes, viscosity regulating substances, pigments, Fillers such as titanium oxide, barium sulfate, chalk, carbon black, dyes, UV absorbers, Stabilizers against thermal or oxidative degradation are used.

Catalysts such as N, N-dimethylbenzylamine, N-methylmorpholine, dibutyltin dilaurate, DABCO (diazabicyclooctane) and desiccants are used. Such siccatives are, for example in Ullmann, Encyclopedia of Technical Chemistry, 4th edition, volume 23 Page 421 (dry matter) Verlag Chemie 1983, and in DE-A-4 032 546 and writings cited therein. Examples include cobalt, lead, magnesium, Zirconium, aluminum, manganese, calcium, cerium, copper, nickel, Vanadium-, barium- and zinc siccatives as well as mixtures called.

The binders according to the invention can be used in coating materials for coating any substrates such as wood, plastics, leather, Paper, textiles, glass, ceramics, plaster, masonry, metals or concrete are used become. They can be applied using standard application methods such as spraying, brushing, Apply flooding, pouring, dipping, rolling. The coating agents can used in the form of clear lacquers as well as in the form of pigmented lacquers become.

The coating combinations according to the invention are surprising low blister susceptibility even in thick coatings. Advantageous is also their direct usability on basic substrates, such as Concrete.

All information in "parts" and "%" refer to the weight.

Example 1 (Production of a Polyisocyanate Component a) to be Used According to the Invention

815.4 g (3.0 mol) of HD-Ocenol 110/130 (product of Henkel KGaA, OHZ: 200-220, iodine number: 110-130, approx. 95% hydrocarbon chains with 18 carbon atoms) are placed in a stirring apparatus flushed with nitrogen. submitted and treated at 70 ° C with 168 g (1.0 mol) of 1,6-hexamethylene diisocyanate. After a reaction time of about 3 hours at a temperature of 90 ° C., the NCO content of the urethane component formed fell below 0.1%. The allophanatization reaction is then started by adding 1740 g (10.0 mol) of tolylene diisocyanate (TDI, 2.4 to 2.6 isomer ratio = 80:20) and subsequent catalysis with 140 mg of zinc stearate at 88 ° C. After 9 hours, the reaction is terminated by adding 140 mg of isophthaloyl dichloride with an NCO content of 24.2%. The excess tolylene diisocyanate is then separated off by thin-layer distillation in a high vacuum (0.1-0.3 mbar) at a temperature of 150 ° C. Product data: yield 1536 g viscosity 3300 mPas / at 23 ° C Fri. TDI content 0.04% NCO content (i) 9.1% theo. Functionality (ii) 2 Allophanate group content (calculated as C2HN2O3, MW: 101) (iii) 20% Hydrocarbon chain content (iiii) 50%

Example 2 (Production of a Polyisocyanate Component a) to be Used According to the Invention

271.8 g (1.0 mol) of HD-Ocenol 110/130 (see Example 1) are placed in a stirring apparatus flushed with nitrogen and at 90 ° C. with 84 g (0.5 mol) of 1,4-tetramethylene diisocyanate (BDI ) offset. After a reaction time of about 8 hours at a temperature of 95 ° C., the NCO content of the diurethane formed fell to below 0.2%. The allophanatization reaction is then started by adding 870 g (5.0 mol) of TDI (see Example 1) and subsequent catalysis with 60 mg of zinc stearate at 88 ° C. After 5 hours, an NCO content of 30.5% is reached and the reaction is stopped with 120 mg of isophthaloyl dichloride. The excess TDI is then removed by thin-film distillation in a high vacuum (0.1-0.3 mbar) at a temperature of 150 ° C. Product data: yield 488 g viscosity 5000 mPas / at 23 ° C Fri. TDI content <0.03% NCO content (i) 7.9% theo. Functionality (ii) 2 Allophanate group content (calculated as C2HN2O3, MW: 101) (iii) 21% Hydrocarbon chain content (iiii) 52%

Example 3 (Production of a Polyisocyanate Component a) to be Used According to the Invention

In a nitrogen purge, 203.3 g (1.0 mol) tech. Lorol (product of Henkel KGaA, OHZ: 265-275, iodine number: <0.5, hydrocarbon chains with 12 to 18 carbon atoms) with 500 g (0.125 mol) of a polyether produced by propoxylation of propylene glycol and subsequent ethoxylation of the propoxylation product (PO / EO Mixing ratio 79/21, OHZ: 28.5) and 105 g (0.625 mol) of 1,6-hexamethylene diisocyanate were added at 70.degree. After a reaction time of about 13 hours at a temperature of 100 ° C., the NCO content of the diurethane formed fell to below 0.2%. The allophanatization reaction is then started by adding 652.5 g (3.75 mol) of TDI (see Example 1) and subsequent catalysis with 73 mg of zinc stearate at 85 ° C. After 9 hours, an NCO content of 17.3% is reached and the reaction is stopped with 70 mg of isophthaloyl dichloride. The excess TDI is then removed by thin-film distillation in a high vacuum (0.1-0.3 mbar) at a temperature of 140 ° C. Product data: yield 995 g viscosity 7500 mPas / at 23 ° C Fri. TDI content <0.03% NCO content (i) 5.4% theo. Functionality (ii) 2.5 Allophanate group content (calculated as C2HN2O3, MW: 101) (iii) 13% Hydrocarbon chain content (iiii) 19%

Examples 4 and 5 (binder combination according to the invention and comparative test not according to the invention)

The proportions of isocyanate-reactive listed in Table 1 are more reactive in a laboratory dissolver Component b) by intensive mixing with desiccant and Deaerating agent homogenized and after cooling to room temperature with the Polyisocyanate component a) from Example 1 or with the non-inventive Polyisocyanate component Desmodur E 21 mixed and poured out as a test specimen.

Compared to the MDI-based comparison binder combination, the binder combination according to the invention has an extended pot life despite catalysis and can also be cured to form bubble-free, thick-film coatings at high atmospheric humidity. With the comparison binder combination, only highly blistered coatings are accessible even under favorable conditions. Composition of the binder combinations Desmophen 550 U (propylene oxide polyether based on TMP, M: 440, product of Bayer AG, Leverkusen) 100 100 Baylith C-Paste (zeolite, product of Bayer AG, Leverkusen) 10 10 Byk A 530 (deaerating agent, product of Byk-Chemie GmbH, Wesel) 0.4 0.4 Dibutyltin dilaurate (10% in Desmophen 550 U) 2.5 - Polyisocyanate from Example 1 351 Polyisocyanate Desmodur E 21 (NCO: 16%, viscosity 6500mPas, solvent-free MDI polyether prepolymer from Bayer AG, Leverkusen) 182 Processing time in minutes 40 25 Shore D hardness (DIN 53505) 51 54 Curing 20 ° C, 30% relative humidity bubbles severe blistering Curing 30 ° C, 80% relative humidity bubbles foaming

Claims (6)

1. A substantially solvent-free binder combination consisting of

   a) a polyisocyanate component with aromatically attached isocyanate groups and

   b) a solvent-free component with isocyanate-reactive groups,

   c) optionally together with further auxiliary substances and additives,

   characterised in that component a) consists of polyisocyanates containing heteroallophanate groups, which polyisocyanates have

   i) an NCO content of 3 to 16%,

   ii) an average functionality of 1.8 to 4,

   iii) an allophanate group content (calculated as C₂HN₂O₃, MW: 101) of 5 to 35% and

   iiii) a content of hydrocarbon chains (linear, branched, saturated or unsaturated), which are present attached to allophanate groups via oxygen, having an average of 2 to 23 carbon atoms, of 10 to 65%.
2. A binder combination according to claim 1, characterised in that component a) consists of polyisocyanates containing heteroallophanate groups and having

   i) an NCO content of 5 to 13%,

   ii) an average functionality of 1.9 to 3,

   iii) an allophanate group content (calculated as C₂HN₂O₃, MW: 101) of 10 to 23% and

   iiii) a content of hydrocarbon chains (linear, branched, saturated or unsaturated), which are present attached to allophanate groups via oxygen, having an average of 8 to 23 carbon atoms, of 18 to 53%.
3. A process for the production of the polyisocyanate component a) to be used according to claim 1, characterised in that

   a1) a linear aliphatic diisocyanate component of an isocyanate group content of 30 to 60% is reacted with

   a2) a hydroxyl component with a hydrocarbon chain of on average 2 to 23 carbon atoms and an average functionality of below 1.5

   in an NCO/OH ratio of approximately 1 to 0.5 to yield a compound containing urethane groups and allophanate formation with excess quantities of

   a3) an aromatic diisocyanate component of an isocyanate group content of 35 to 53%, wherein the diisocyanate component a3) remaining after the reaction is removed down to a content of below 0.5%.
4. A process for production according to claim 1, characterised in that 2,4- or 2,6-tolylene diisocyanate or mixtures thereof are used as the diisocyanate component a3).
5. Use of the binder combination according to claim 1 as or in two component coating materials.
6. Use of the binder combinations according to claim 1 as a moisture curing coating system to be applied as a single component.